Modern motor vehicles have a windshield cleaning system which in addition to a windshield wiper system also includes a windshield washer system, via which washer system washing liquid is sprayed onto the window pane to be cleaned. Recently constructions have been successful in which the washing liquid is supplied from a bore in the wiper shaft to a nozzle above the wiper arm. A system of this kind is known from the German patent 3 523 441. In this construction a pipe for forming a washing liquid channel is put into the through-going bore of the wiper shaft. A pipe union is integrally formed onto one end of the pipe. A nozzle body is locked with the pipe at its other end projecting over the wiper shaft. The nozzle body has a locking recess cooperating with a crowned locking body formed onto the outer surface of the pipe. A construction of this kind has proven worthwhile in practice. However it has to be stated that a demounting of the nozzle body during a possibly necessary repair is very difficult, if the locking device is constructed in such way, that a satisfactory sealing is achieved in this passage between pipe and nozzle body even after a longer service time. If, however, dimensions and materials for the locking body and for the locking recess on the nozzle body are selected, which enable a locking without exerting a great amount of force, it has to be feared, that washing liquid flows out in this place, in particular if the supply pressure is increased. It is furthermore a disadvantage of the known construction that the pipe cannot be exchanged without difficulty, if a rear window wiper system is concerned in which the wiper shaft is directly integrated into the gear housing of the drive motor.